AQA AS Level Biology Paper 1, November 2021: Question 2

6 marks · Medium difficulty · Short Answer

Name structures A and B of the human immunodeficiency virus (HIV) shown in Figure 2, and describe how HIV is replicated.

Practise this question

Question

Figure 2 shows a diagram of the human immunodeficiency virus (HIV) with labels A pointing to a surface glycoprotein/attachment protein and B pointing to the capsid enclosing the viral genetic material. Sub-question 02.1 asks to name structures A and B. Sub-question 02.2 asks to describe how HIV is replicated.
Question text

02 Figure 2 shows the structure of the human immunodeficiency virus (HIV).

Figure 2

02.1 Name structures A and B.

[2 marks]

A

B

02.2 Describe how HIV is replicated.

[4 marks]

Mark scheme

Show the mark scheme The mark scheme for question 02.1 awards 1 mark for A as attachment protein (or gp41/gp120) and 1 mark for B as capsid (or capsomere/protein). The mark scheme for question 02.2 awards up to 4 marks for detailing HIV replication: attachment protein binds to helper T cell receptors, RNA enters cell, reverse transcriptase converts RNA to DNA, viral proteins/enzymes produced, and virus particles assembled and released.

Question Marking Guidance Mark Comments

02.1 1. A = Attachment protein; 1. Accept gp41

/gp140

2. B = Capsid /gp120/CD4/

glycoprotein

OR

2 1. Accept antigen

Capsomere

1. Ignore receptor

OR protein

Protein;

02.2 1. Attachment proteins attach to receptors on helper

T cell/lymphocyte;

2. Nucleic acid/RNA enters cell;

3. Reverse transcriptase converts RNA to DNA; 4 max

4. Viral protein/capsid/enzymes produced;

5. Virus (particles) assembled and released (from

cell);

TOTAL 6

How to answer it

Structure and Replication of HIV

What this question tests

This question assesses your knowledge of viral ultrastructure and the step-by-step molecular mechanism of retroviral replication. You must recall specific biological terminology for viral components and accurately sequence the events from host cell entry to viral particle release.

Question 02.1 - [2 marks]

Name structures A and B.

✅ Correct Answer

  • A: Attachment protein (Accept: glycoprotein, gp41, gp120, antigen. Ignore: receptor protein)
  • B: Capsid (Accept: capsomere, protein)

💡 Key Knowledge

  • Attachment proteins (A): Project from the viral envelope and are essential for binding to complementary receptors on host cells.
  • Capsid (B): The protein coat enclosing the viral genetic material (RNA) and vital enzymes like reverse transcriptase.

🧠 Exam Technique

  • Keep answers concise and direct. Do not write full sentences for naming questions.
  • Ensure you distinguish between the outer envelope glycoproteins (attachment proteins) and internal structural proteins.

❌ Common Errors

  • Confusing the attachment protein with the host cell receptor. Remember, the *virus* has attachment proteins; the *host cell* has receptors.
  • Writing vague terms like "membrane" instead of identifying specific structures.
Mark Breakdown: 1 mark for A, 1 mark for B. Total = 2 marks.
Question 02.2 - [4 marks max]

Describe how HIV is replicated.

✅ Correct Answer (Mark Scheme Points)

  • 1. Attachment proteins attach to receptors on helper T cell / lymphocyte.
  • 2. Nucleic acid / RNA enters the cell.
  • 3. Reverse transcriptase converts RNA to DNA.
  • 4. Viral protein / capsid / enzymes produced.
  • 5. Virus particles assembled and released (from cell).

💡 Key Knowledge

  • As a retrovirus, HIV uses reverse transcriptase to create complementary DNA (cDNA) from its viral RNA template.
  • The newly made viral DNA is then integrated into the host cell's genome, allowing host machinery to transcribe and translate viral proteins.

🧠 Exam Technique

  • This is a "describe" process question. Write points in chronological order to mirror the biological timeline.
  • Use precise terminology: specify helper T cells rather than just "cells", and state reverse transcriptase rather than just "enzymes".

❌ Common Errors

  • Stating that HIV replicates independently—viruses cannot replicate without a host cell.
  • Saying that RNA is converted straight into proteins, missing the crucial intermediate step of reverse transcription into DNA.
Mark Breakdown: Awarded as marking points up to a maximum of 4 marks. Clear sequential progression is key to securing full marks.

Topics

Biology · 3.2 Cells

Question and mark scheme from the AQA AS Level Biology examination, Paper 1, November 2021. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.